Four candidates vying to be the 2nd Congressional District Democratic candidate this fall will take part in a debate a week before the primary election.The debate will be at 7 p.m. Aug. 7 in the H.F. DeLuca Forum in the Wisconsin Institutes for Discovery on the UW-Madison campus, according to a news release from UW-Madison.The four candidates are state Reps. Mark Pocan and Kelda Roys, Iraq war veteran Matt Silverman and consultant Dennis Hall.